[Libevent-users] bug in event_base_free()

[Andrei Nigmatulin]

Hello, list

Please consider my application:

1. There is one process that always in event loop (master process).
2. By some event it forks and create "child" process, that call 
event_exit_loop() and after event_loop() exits it try to clean up everything 
associated with libevent.
3. For this purpose child call event_base_free(), but it have to remove all 
events that was added by parent before fork happened. Otherwise it will be 
hit by assert(TAILQ_EMPTY(&base->eventqueue)).
4. With poll or select methods there no problems with deleting events at this 
point.
5. But with epoll, kqueue or event ports methods the child and the parent 
shares *same* event device and set of file descriptors after fork(). So if 
child call event_del() on every event that was added before in parent, events 
are also deleted from parent's device (actually, the same device), which is 
absolutely not what I want.

Thus, there is only one way to deal with it: child must not call 
event_base_free() and must live with opened event device.

Attached diff provides a fix for this situation. I believe process must not 
check if base->eventqueue and other queues are empty. Calling 
evsel->dealloc() is enough to remove all events.



-- 
Andrei Nigmatulin
GPG PUB KEY 6449830D

Now I lay me down to sleep(3)
Pray the OS my core to keep
If I die before I wake
Pray the Disk my core to take
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